Source : Webster's Revised Unabridged Dictionary (1913)

Boycott \Boy"cott`\, v. t. [imp. & p. p. {Boycotted}; p. pr. &
   vb. n. {Boycotting}.] [From Captain Boycott, a land agent in
   Mayo, Ireland, so treated in 1880.]
   To combine against (a landlord, tradesman, employer, or other
   person), to withhold social or business relations from him,
   and to deter others from holding such relations; to subject
   to a boycott.

Boycott \Boy"cott\, n.
   The process, fact, or pressure of boycotting; a combining to
   withhold or prevent dealing or social intercourse with a
   tradesman, employer, etc.; social and business interdiction
   for the purpose of coercion.

Source : WordNet®

boycott
     n : a group's refusal to have commercial dealings with some
         organization in protest against its policies
     v : refuse to sponsor; refuse to do business with [ant: {patronize},
          {patronize}]